Electrostatic printer with scanning dielectric segment

ABSTRACT

A high-speed electrostatic printing mechanism including a hollow-type roll presenting a concave matrix of raised font electrodes, the electrodes being configured as different alphanumeric print characters; and, arranged in image-able relation with the electrode array, a plurality of dielectric segments, each of approximately &#39;&#39;&#39;&#39;printline height&#39;&#39;&#39;&#39; and mounted on a propeller arm to be swept past the concave matrix for receiving character images therefrom.

ll United States Patent 1 1 3,569,982

[72] Inventors Michael S. Shebanow; [56] References Cited Ronald F. Borelli, Medfield, Mass. UNITED STATES PATENTS P 695176 3,023,731 3/1962 Schwertz 346/74X gf 5 3 3,316,555 4/1967 Barish 346/74 1 v Assignee Honeywell Inc. 3,348,232 10/1967 Kmg 346/74 Minneapolis, Minn. Primary Examiner-Bernard Konick Assistant Examiner-Gary M. Hoffman Attorney-Fred Jacob ABSTRACT: A high-speed electrostatic printing mechanism [54] WITH SCANNING including a hollow-type roll presenting a concave matrix of 20 Cl 16 D raised font electrodes, the electrodes being configured as difrawmg ferent alphanumeric print characters; and, arranged in image- [52] [1.8. CI 346/74 able relation with the electrode array, a plurality of dielectric [51] lnt.C|I ...G0ld 15/06 segments, each of approximately printline height and [50] Field of Search 346/74 mounted on a propeller arm to be swept past the concave (ES), (ESX), (E); lOl/(ESD) matrix for receiving character images therefrom.

PATENTEB m 9 I97! SHEET 1 [1F 4 INVENTORS NALD F. BORELLI CHAEL S. SHEBANOW WW M ATTORNEY PATENTEU MAR 9 Ian SHEET 2 0F 4 STRIP SELECT INVENTORS F. BORELLI MICHAEL S. SHEBANOW RONALD PATENTED MAR 9 I971 SHEET 3 0F 4 fiy- W M ATTORNEY PATENTEDMAR 9m 3,569,982

SHEET k 0F 4 INVENTORS RONALD F. BORELLI Y MICHAEL S. SHEBANOW FIG. HA a ATTORNEY ELECTRQSTATEC HUNTER Wll'lkll SCANNING DIELECTRIC SEGMENT INVENTION FEATURES, PROBLEMS In the high speed printer art, as adapted for computer printout or the like, workers have long tried to eliminate the impacting mechanisms of conventional printers for several important reasons, such as noise reduction, increased print speed, elimination of problems in manufacturing and maintenance and other reasons associated with the undesirability of using moving mechanical elements such as striking elements, scraping surfaces and so on. As a result, some workers have turned to electrostatic imaging as a solution; representative efforts being disclosed, for instance, in U.S. Pat. No. 2,919,967 and 3,045,587 (both to Schwertz) and U.S. Pat. No. 3,182,333 (to Amada et al.). Some prior art efforts have involved impressing an electrostatic image on a photoconductive medium; others, to produce faster imaging, have turned to electroprinting (sometimes called Tesi-printing) whereby a latent electrostatic charge pattern is deposited on an insulatingrecording medium by virtue of an ionizing field discharge between two electrodes, one electrode being shaped as a prescribed character (one of a set). Of course, the imaging medium must be a sufficiently good dielectric not to break down upon application of the image-charge until the image transfer is effected, this. being done, typically, by application of a (relatively low-voltage) triggering pulse to one or both electrodes surrounding the dielectric. Electronic switching circuits and memory elements are typically contemplated for selectively printing in accordance with information received; for instance, from a digital computer, or analogous printer control source. Typically, these images are developed with toner material and thereafter transferred (electrostatically, preferably; or by contact) to copy paper. Some less desirable systems apply a corona charge to the transfer sheet, though this can degenerate the electrostatic image due to the breakdown of the air layer between the sheet and the dielectric. A cautionary observation is that when the dielectric and transfer sheet are in virtual contact, the airfilm separation between them is so small (from a few microns to a few mils) that an extremely high potential is required to trigger air-breakdown; but as this spacing increases, much smaller fields can initiate breakdown (ion avalanche) and badly distort the latent electrostatic image, making it unacceptable for reuse.

Prior art forms of electroprinting, such as those aforementioned, have typically involved the use of raised font character-electrodes in the form of a cylindrical-type wheel or drum, the font being distributed circumferentially thereabout in the manner of conventional high speed (impact) printers. With the present invention, however, the character-electrode array is presented in a hollow-type roll configuration with the charactenelectrodes distributed uniformly about a regular concave font-imaging plane along which a dielectric recording medium can be swept for imaging. According to a prime feature of the invention, such a dielectric is made, effectively, a row-height segment mounted upon a propeller arm to be so swept, the arm also constituting the ground plane and the character matrix preferably comprising a set of multicharacter electrode strips, the selective energization of which synchronous with the passing dielectric, effects a selective imaging at prescribed column locations. Thus, the font array is kept stationary and need not be rotated, commutated, etc. as is conventional. More importantly and according to another prime feature, the dielectric medium may comprise a centrally located dielectric buffer record which may serve as the focal point around which a number of dielectric treating (imaging and transferring) stations (e.g. a plurality of printout stations) may be very conveniently arranged-something entirely new in the art. Further, where a number of printout stations are provided, there is no necessity for a plurality of imaging stations; rather, the same image can be transferred a number of times at all printout stations (perhaps being enhanced, toned,

etc. in the interim). Workers in the art will appreciate that as a result of this arrangement, high speed printer apparatus is provided to be operable with a smaller, more compact transport drum, this drum (or propeller") also serving as an imaging carrier and operated within the diameter of the described concave electrode plane. Those skilled in the art will recognize several important advantages accruing to such a hollow-type roll-segmented dielectric" combination, such as improved access to the character-electrodes, these i being presented directly to external connections whereas with prior art configurations they would have to be accessed from within a continualIy-rotating type roll (obviously involving some rather nasty complications, such as how to arrange intraroll conductors, how to insulate them and lead them out through a rotating hub, plus commutation problems associated with applying power along multiple parallel lines through a revolving hub, etc.). Another advantage recognized will be that a more convenient, compact font array is presented for page-imaging; this generally being impractical with a conventional-type roll. An associated advantage is that this arrangement provides a very convenient means for line-at-a-time" imaging, such as on unit record dielectric media, whereby a single printline may be imaged with each rotational pass ofv a rotary carrier. Yet another important advantage is that a dielectric coated drum may be used as the recording medium for the hollow-type roll array whereas this is impractical with conventional-type rolls.

Another, very important, advantage is that (as suggested above) such a centrally-disposed dielectric may serve as the focus" for a number of separate, multitreatment imagingcopying stations, where heretofore workers in the art have been compelled to provide totally separate apparatus, inline for imaging, recording, etc., with the attendant difficulty of (mechanically or electronically) synchronizing their operation (and often involving elaborate separate controls for each which are not required here).

According to another feature of the invention, with the aforementioned raised font characters so provided as a set of electrically-independent conductor strips, a (single row") dielectric segment may be mechanically-scanned for imaging. That is, the dielectric segment may be swept past this concave matrix of multielectrode strips in prescribed synchronism so that vertical-electrode-selection (typically Y selection" in the prior art) may be dispensed with along with its dependent drivers selection means, etc. the selection being made simply according to the timing of strip-energization during the sweeping scan of the dielectric. Workers in the art will appreciate the tremendous cost savings and simplication advantages of such a mechanical scanning feature. Also, switching problems and interconnection complexity will be reduced since, rather than requiring a typical 64 X 132 matrix of character electrodes with all the associated circuitry such as drivers, connections, switching means, etc., these expensive stages may be reduced by a factor of 64:1 since all character-electrodes in a column are presented on a single common electrode-strip which, in turn, requires only one such selection means, driver connections etc. (rather than 64 or one circuit for each character).

According to a desirable subfeature of the invention, such single row dielectric segments may, of themselves, initiate the advance of the copy medium, either directly by contacting it and rolling it themselves, or indirectly, via an extension of their rotary carrier (rotating therewith). Workers in the art will appreciate that, by effectively rolling the dielectric across the copy paper, this feature can minimize smear and smudging (since there should be no relative dielectric-copy motion) and that the system will be self-synchronizing etc. According to a modified form of this single row" segmented dielectric, the dielectric layer may be made as large as convenient and the singlerow-segment defined by a segmented back-electrode, such as a conductive ground plane portion of a drum onto which the dielectric is continuously coated.

Therefore, it is an important object of the present invention to provide a nonimpact electrostatic high speed printing mechanism for computer printout and the like. It is a related object to provide such a mechanism with the aforementioned features and advantages and solving the aforementioned problems. Another object is to provide such a printing mechanism for Tesi-printing by effectively scanning a single row-segment of the dielectric past an outer concentrically disposed matrix of character electrodes. A further object is to allow such printing in a noncontact mode.

Other objects and advantages will appear as the description proceeds. In accordance with one embodiment of the invention described in detail below, a stationary matrix of font electrodes is arrayed along a prescribed concave imaging plane for Tesi-printingwith at least one single row, buffer dielectric segment provided on a ground plane propeller arm adapted to sweep this segment past the matrix for mechanically scanning and imaging a row of print images electrostatically, one row for each such scan if desired.

For a better understanding of the invention, as well as other objects and further features thereof, reference should be had to the following detailed description of preferred embodiments thereof, together with the accompanying drawings wherein like reference symbols denote like parts and wherein:

FIG. 1 is a very schematic isometric of an electroprinting embodiment comprising a concave font-matrix, a set of print stations comprising an imaging station, a developing station, a copy station and related controls, together with an inner central pair of propeller blades each carrying buffer dielectric segments to be swept in operative relation past these stations and transfer to a copy web as indicated;

FIG. 1A is a highly schematic side view of an embodiment after FIG. 1, illustrating three successive rotational positions of the two-blade propeller exemplarily;

FIG. 2 shows an alternate embodiment to that in FIGS. 1 and IA wherein dielectric substrate segments are carried upon the continuous periphery of a drum and a pair of print-station sets, each set analogous to the set in FIG. 1, are indicated, these sets being disposed radially about this drum;

FIG. 3 indicates another alternate embodiment with a carrier drum similar to that in FIG. 2 but somewhat modified so that a continuous dielectric is arranged thereon with a single row image segments being defined by ground plane electrodes in the drum, these electrodes being selectively charged;

FIG. 4 is a fragmentary section of an alternate embodiment similar to that in FIGS. 2 and 3 modified, however, so that the ground plane electrodes comprise separately rotatable conductor blades, in operative relation with a peripherally-adjacent dielectric web on a separately rotatable carried drum; FIG. 4A being a longitudinal section through FIG. 4;

FIG. 5 is another alternate embodiment similar to 4 but slightly modified so that the rotating ground blade resiliently thrusts a related dielectric confronting segment into operating relation with the font electrode plane;

FIG. 6 is another alternate embodiment similar to that in FIG. 2 but modified somewhat so that, instead of a number of ground plane segments, a single-row-exposing discharge mask is interposed between font-matrix and dielectric, and scanned therepast;

FIG. 7 is a highly simplified, schematic isometric of a dielectric drum similar to that in FIG. 2, but modified somewhat to incorporate an associated sectorial pair of copy-web advancing blades; FIG. 7A indicating this arrangement in cross-sectional view;

FIG. 8 is a side sectional view of another modified embodiment indicating a printing arrangement functionally similar to that of FIG. 2 however, with the added improvement feature of a multipass, copy-advancing drum for imaging an entire page document in repeated passes, this drum being so dimensioned and mechanically coupled to rotate in synchronism with the dielectric carrier as to effect printout on successive rows automatically;

FIG. 9 is an idealized isometric of a different font-electrode imaging arrangement from the foregoing concave matrix, including a novel set of individual character-wheel electrodes,

electrically independent, but rotated together, past an novel associated capacitive-charging electrode and thence, into imaging adjacency with an image dielectric medium; FIG. 9A a timing diagram, indicating a pair of representative charging cycles for two such character wheels;

FIG. 10 is a modified embodiment of a character-imaging electrode matrix functionally similar to that indicated in FIG. I, but greatly modified and simplified so that a prescribed set of adjacent font columns comprise a single (multifont-set) electrode strip, each columnar segment thereof staggered circumferentially about the scanning path of the dielectric and arranged to share a common select-driver means, as indicated in a highly idealized fragmentary manner;

FIG. I1 is a schematic view of an arrangement similar to that in FIG. 10, somewhat modified, however, to indicate a single mark-imaging" strip electrode with a set of markdefining, column-registered raised electrode blocks thereon, each being offset with respect to all others to define a blockarray staggered diagonally acrossa concave font-plane so as to be sequentially column-registered at the dielectric and to share a single select means for all columns, after the manner indicated for each strip-set in FIG. 10; and

FIG. 11A is a fragmentaryschematic isometric of a markimaging head module, such as to be used in FIG. ll prior to final assembly, machining, etc. thereof.

DIELECTRIC PROPELLERS By way of indicating a concave matrix of font-electrodes in electrostatic imaging (Tesi-imaging) relation with a pair of dielectric carrier propeller blades, the embodiment shown in FIGS. I and IA will now be described. According to this feature of the invention, this arrangement comprises a concave cylindrical font-plane defined by an array I-M of individual raised font character electrodes (ce); only an exemplary few thereof being shown with a full character set, e.g. I32 X 62,

font-electrodes being understood, each character-column therein being electrically separate and integral, preferably comprising a column-electrode strip l-M-l, etc. According to a prime feature of this embodiment, this font-array is arranged in operative imaging relation with a dielectric-coated imaging carrier comprising a pair of opposed carrier blades I-D, rotatably mounted to be concentrically within imaging array I-M and to present a pair of thin dielectric coating segments IDL, l-DL' in operative, image-able, relation l-M. Carrier 1-D will be understood to also operatively associate segments DL, DL with a toning roll l-TR, an erasing roll l-C and a copy-transfer roll I-CR (See FIG. IA). Transfer roll l-CR selectably presents copy (paper) media I-CM row-by-row, in transfer relation with dielectric segments DL, DL' after imaging and toning thereof as generally known in the art. Workers in the art will understand the general construction and operation of these elements; however, for further details, especially of the structure and operation of matrix I-M, reference is made to copending commonly-assigned US. Pat. application Ser. No. 679,89l,filed Nov. 1, 1967.

One important feature of the invention is that one or more such dielectric segments may thus mechanically scan matrix I-M and thereby simplify things, e.g. dispensing with means for synchronizing imaging with passage of a dielectric row. Imaging matrix I-M of character-electrodes is arranged to render each columnar electrode strip (e.g. l-M-l etc.) electrically independent of all others, each being selectively energized by an associated individual connector portion of cable ll-CN from select unit l-CS (e.g. connector CN-l from strip l-M-I) to an associate select-driver section of I-CS), most of the usual number of select drivers, connectors, etc. being eliminated, as aforementioned. Of course, array l-M presents a' complete set of such (alphanumeric character imaging) electrodes along each column of the printline" juncture with segments 1-DL (i.e. along the imaging plane), there being as many electrode strips as there are columns to be printed (i.e. print-positions along segment DL-l and on copy media I-CM etc.). The raised electrode font for each character will be aligned along a respective row R1, R6 etc., there being, thus, as many rows as there are different characters in the set (only a few representative rows and columns being shown by way of illustration). As understood in the art, a great many drivers would conventionally be required (e.g. a 132 X 64 array of select-drivers, connectors, etc. for 132 print columns with 64 different character fonts) to couple each font to the Select means l-CS as understood by those skilled in the art. For instance, select control units l-CS would typically comprise a memory-control unit for a high speed (computer-coupled) printer control being adapted for impressing a print-pulse" voltage on a particular column electrode registered with an as-' sociated print-column position on dielectric segment DL, doing so, according to the invention, only where that segment is image-registered with the row of this electrode corresponding to selected character location.

Conductive carrier shaft l-DA is arranged to apply a prescribed reference potential V (e.g. ground) to the dielectric segments, this hub being rotated by conventional means (not shown) applied to drive it at a prescribed constant dielectric surface velocity (for 1-DL, l-DL'). A conventional Character Code Generator unit (known in the art and schematically indicated as code wheel CW and code detector CCG) is arranged to supply strobe signals cc to select unit l-CS indicating the character-row (on matrix l-M) past which either dielectric segment is being swept. Workers in the art will understand that when strobe signals cc are applied to a strip-select stage SS in control unit l-CS and compared to print-signals SlG (conventionally applied at input stage [S of unit ll-CS) various hit-bit signals will be generated and applied to drive corresponding column drivers in strip-driver stage SD, at respective times.

in one advantageous mode of operating this system, a particular (variable) angular section M (see FIG. 1A) is appropriated for imaging printlines, along which the segments DL may be scanned. Then, as segments DL are swept past successive character-rows r-l to r-n of imaging matrix l-M (cf. condition ll of segment 1-DL), an imaging potential may be applied to the appropriate column electrode along each respective column l-M-l through ll-M-N as the corresponding character-rows r pass by. Sector M" may be varied in extent; for instance, so that successive printlines may be generated in relatively close succession, with the imaging of a following line beginning hard upon an indication (signal) of imaging-complete" for a subject line on a segment, the propeller arrangement being accordingly modified (e.g. adding another propeller arm, etc.).

Thereafter, the so-imaged printline will be toned at station l-TR (position ill for l-DL'), which may comprise any known implementation suitable, such as a roll-toner arrangemerit, a magnetic brush developer (e.g. with magnetic carrier heads) or the like, as known in the art. Following this, with propeller 3-D kept rotating constantly, the so-toned imageline is then brought into transfer-relation with copy roll l-CR and copy paper li-CM thereon, so as to transfer the toned image to medium l-CM. Paper LCM may comprise ordinary untreated paper, unspooled from supply roll l-S and driven along with the toned layer (l-DL) at the same surface velocity (e.g. by propeller 1-D or otherwise, as discussed below). Successive copies may be'made, if desired, by recirculating this toned line-image on l-DL past another copy-out station or through a second complete cycle without erasing, imaging or necessarily retoning (if the time delay for this can be tolerated), therewhile disabling the clean erase station 1-C etc. for this period and retoning at ll-TR, if desired, etc. The toner image may be fused on l-CM in a conventional manner, such as by heating at copy fuser station l-F as understood in the art. Thereafter, the residue of the toned image on the dielectric will normally be swept past erase station l-C (e.g. see layer l- DL at position III), for cleaning (toner removal) and electrostatic neutralizing (image-erase) as known in the art. Of course, a plurality of lines might also be imaged for subsequent simultaneous development and copy-out where the associated complications could be tolerated; such as the appropriately large memory and high speed switching means which would typically be needed, as known in the art; however, this would sacrifice most advantages.

With respect to imaging and transferring and the voltage control therefor, the following will be understood. The hit pulses applied to strips 1-Ml etc. will comprise a prescribed imaging voltage VS) of prescribed duration, (approximating the time-dwell of the respective dielectric segment DL registering with the corresponding selected character-row). Paper advance roller l-CR is preferably made conductive and charged with a prescribed transfer voltage V-, for attracting the partly charged toner particles onto the copy medium l-CM, although a rolling-contact transfer may be made with or without this potential applied in certain cases (this mode of transfer being another distinctive advantage of the propeller embodiment and mentioned below in connection with the driving of the medium by the propeller arm). As known in the art, a neutralizing potential is also applied (-V-) at the cleaning station l-C to erase the electrostatic image on the passing dielectric preparatory to sweeping it past the matrix l-M for a new imaging cycle. Polarities will conveniently be kept appropriate; e.g. V will be positive, if the electrostatic image (esi) is to be negative; and, hence, the toner applied is preferably charged (positive); the transfer potential V will be negative and the cleaning potential positive.

Another advantageous feature related to the foregoing propeller arm type dielectric carrier relates to copy paper advancement thereby and is discussed elsewhere below. That is,

it will be understood that with a proper disposition of the dielectric layer (l-DL,- l-DL), any other projection from such a propeller arm, against copy medium l-CM, the advancement of the arm past the transfer point may, quite readily, act to advance this medium. For instance, the (toned) dielectric may be frictionally engaged with the medium l-CM to engage it therewith in a rolling contact" transfer action, quite advantageous for good (nonslip) toner transfer as well as apt for advancing l-CM the while. in such a case, the dielectric surface will be understood as made sufficiently hard.(and tough, abrasion-resistant, drum adherent, etc.) to satisfactorily perform without degradation (while still accepting a satisfactory esi in the environment of course). To ameliorate this rolling-contact" the copy-presenting roll l-CR may of course be provided with a compliant surface; even being covered with a soft rubber blanket (e.g. like those associated with offset printing-such a covering may also, itself, accept the toner pattern and transfer it to copy media thereafter).

FIG. 2 shows in cross-sectional (somewhat idealized)'form, an arrangement similar to that in H6. 1A and understood as similarly structured and operating except for the following modification features. According to one of these features, the dielectric DL is mounted on a continuous conductive drum 2 D, rather than upon separate propeller arms of FIGS. 1, IA, this arrangement being a satisfactory alternative in certain cases, such as where it is preferable to drive a drum carrier rather than a propeller arm. Here, every dielectric segment (there may be more than one) is understood as disposed on the drum in prescribed circumferential relation, such as segments DLll, DL-2 disposed in prescribed opposing relation; e.g. so as to synchronously register with opposed corresponding imaging matrices Z-M-l, 2-M-2 (and with the other treatment stations if desired). Dielectric segments DL-ll, DL,-2 are functionally the same as those noted above (e.g. being a single row in height, etc. except where noted). It will be apparent that any number of such segments may be disposed on drum 2-D consistent with the desired drum diameter, the number of (duplicated) imaging-copying stations desired, etc.

According to a second modification feature of this embodiment, a second set of printing stations (duplicating stations 2-M-1; TR-l; CM-l; CL-li) is taught; of course, more may be provided as workers in t Ifia Krt can imagine, these being made feasible according to the aforedescribed central focused) location of the buffer dielectric. Thus, note that segments DL-l, DL-Z serve as a focus"of which the several treatment stations shown are disposed radially, in the manner of satellites. Thus, one such print station set comprises Tesiimaging matrix Z-M-l, controlled by signals from a select means CS (not shown), toner station TR-l, copy station TM-ll, and cleaning station CL-ll, indicated as disposed about an arcuate sector S, of the cylindrical dielectric path (the matrix occupying a sector in M,) these stations being understood as generally equivalent to the corresponding stations in FIGS. l, llA above. A second similar print station set comprises similar stations; namely, matrix -2-M-2, toner station TR-Z, copy station CM-2 and cleaning station CL-IZ may be similarly provided, preferably in prescribed circumferential relation with the corresponding stations of the first set (e.g. enabling contemporaneous control of both). That is, it will appear as another unique advantage of the invention that, if the second matrix 2f-M-2 is disposed so that successive rows thereof register with one associated dielectric segment (e.g. DL-2) at the same time that the corresponding rows of the companion matrix 2-M-l register with the other dielectric segment (Db-1), it will be apparent that a number of advantages may be derived. For instance, workers in the art will appreciate that this can facilitate simplified two-copy printout in that a common select-driver means CS may be applied to control imaging of both segments (charging the two corresponding column-electrode strips in each matrix) so as to produce electrostatic output at two stations rather. than one and thus provide copy printout automatically with a minimum of added hardware, control logic etc. One advantageous feature allowing this will be that the fixed locations of matrices 2-M-1 and 2-M2 together with the fixed locations of dielectric segments DL on the periphery of the common drum carrier will guarantee that synchronism of registry will always be maintained, whereas, in the prior art, additional complicated mechanical electronic synchronizing means are necessary for this; moreover, such means customarily operate with questionable reliability. Of course, consistent with the dictates of space, etc., other copy stations may be duplicated about the periphery of drum 2-D according to this feature of the invention.

FIG. 3 is a showing similar to that of FIG. 2 and may be understood as operating similarly except where indicated for certain modification features. Here, a continuously-rotated (dielectric carrier) drum 3!) is arranged to sweep dielectric thereon successively past an associated character-electrode matrix 3-M like matrix i-M (eg. comprising electrode strips, each selectively controlled from a strip select means in the foregoing manner). Similarly, a toner station is provided at toning roller 3-T and a copy-out station provided at paper drive roller 3-! for guided advancement of a copy web 3-CM into transfer adjacency with the toner image on the dielectric, and therebeyond, to be fixed (as before) at fixing station S-F. A cleaning-neutralizing station is also provided at cleaning roll 3-CL, all these elements being understood as generally constructed and operated in the aforedescribed manner.

According to one modification feature, the dielectric coating DD-C on drum 3-D is in a continuous layer form (rather than a segmented or discontinuous form as above) and various ground electrode substrates e are provided beneath the dielectric layer to, themselves, define respective single row imaging segments, (of DD-C) being conductive and connected to a prescribed ground potential V,, while the rest of drum 3-D is nonconductive. More particularly, each such ground electrode (such as ground electrode e-l shown confronting the A row of matrix 3-M) will be understood as similar in cross-sectional configuration to dielectric segments l-DL in FIGS. 1, 1A (or segments DL-l etc. in FIG. 2) corresponding approximately in height and length to a printline. Ground electrode e-ll may be understood as connected to a source of ground potential, such as a grounded hub analogous to shaft l-DA in FIG. 1. As in the foregoing cases, it may be desired to have a plurality of such imaging segments on drum 3-D, such as the second, third and fourth ground electrodes e-2, 2-3, e-4, each spaced from one another a prescribed arcuate sector M (corresponding approximately to the sector of thematrix 3-M), all being connected into a common ground conductor hub (as indicated by the schematized ring) and each defining a respective image-segment portion of layer DD-C. Workers in the art will appreciate, in light of the foregoing, that the use of four such ground electrodes may be preferable and more efficient in certain cases; for example, enabling drum 3-D to transfer a line of toned-image print to medium 3-CM for every of drum rotation (four lines per revolution); Of course, this does not have to be the mode of transfer; for instance, images may be generated and developed at all four ground electrode locations during one revolution and then transferred to output medium 3-CM during a succeeding revolution, etc.

Moreover, according to a useful advantage, and an improvement feature of this embodiment, a higher printline density may be achieved about the periphery of drum 3-D by providing a number of differently-energized (switched selectively) ground electrodes within each matrix sector (M"). For instance, a first alternate set of alternate electrodes e is indicated in phantom as spaced approximately two rows from the aforementioned electrodes e (shown in full); namely, first alternate electrodes e'-l,- e'-2, e'-3, e-4. All these 2 electrodes will be understood as connected to a common ring connector which, in turn, may be selectively switched to be energized by the ground electrode (for instance, during a following revolution of drum 3-D, after the revolution for imaging at the primary electrodes e). Of course, such alternate electrode set cannot be energized contemporaneous with a companion set but rather selectively; that is the electrodes of set e cannot be energized contemporaneous with electrode set 2, while both are sweeping past matrix 3-M, since otherwise the selection feature inherent in this mechanical scanning would be lost (i.e. only one electrode energized while a given sector, M is scanning the matrix). In a similar manner, a tertiary set of alternate ground electrodes 2" is exemplarily shown, spaced about two rows downstream of the aforementioned secondary electrodes 2; namely, electrodes e"-1, e"-2, e"-3, e"4, all electrically coupled to a common connector ring which may be selectively switched to carry the ground potential only during a selected tertiary revolution". in this manner, it will be apparent to those skilled in the art that more than a single line of print may be imaged in any given sector (M") of drum 3-D; indeed, the entire surface of the drum may be effectively covered with imaged (and developed) printlines, if sufficient alternate electrode sets are provided (and if successive revolutions can be tolerated, etc.). Many consequential advantages will occur to those skilled in the art, such as the ability to image and develop a plurality of printlines before copytransfer thereof. For instance, if sufficient memory and control means are provided, four successive pages of print could be imaged about the periphery of drum 3-D and then be developed and copy-transferred in one revolution (page-at-atime). Thus, a first memory could be accessed to image a first line of print while primary electrode e -1 starts to scan matrix 3-M; then a second memory for a second page of print, first line thereof, could be accessed to image the first line on the next primary electrode e-4 as it scans 3-M, and so on for the first ofa third page on e-3 and the first line of a fourth page on e-2, all during the first revolution of drum 3-D with the same four memory units being shifted one line and successively accessed during the next revolution. Thus, next the second line of print is imaged on the next adjacent (secondary) ground electrode set; and similarly for the third line, for the fourth line, etc. of all four pages. Each page (set of print lines) would fill a sector M" and when the entire page(s) is imaged it could all be toned (at toner roll 3-T) and transferred (at copytransfer station 3-K) during one pass, the cleaning station 3-CL then operating; these stations being disabled otherwise (e.g. during these imaging revolutions-N revolutions corresponding to N lines for eachpyge). In this way, the transfer of all four pages of print successively to medium 3-CM could be simply effected from the same buffer dielectric. Of course, the system will have to be arranged to not only tolerate the moderate complexity (e.g. memory accessing and storage) of this mode of operation, but also the somewhat periodic printout it entails.

FIGS. 4 and 4A show a fragmentary section of an arrangement substantially the same as that in FIG. 3 except for a modification feature whereby the ground electrode (or electrodes) are mounted independently and are independently charged, much in the manner of propeller arms in FIGS. 1,

1A. That is, each ground electrode GP is disposed within the axial confines of a carrier drum 4-D (pair of end-hubs thereof) carrying the dielectric medium (M, in phantom) in any engaged relation to advance it past an imaging-font-plane (FP) plane to be selectively imaged (esi) thereby as before. The outermost (radial) periphery of propeller electrode GP is arranged to contact a prescribed line segment of the medium and sweep with it past imaging plane FP in the foregoing manner.FlG. 4A (a longitudinal section of the arrangement in FIG. 4) best shows the dielectric carrier comprising the pair of outboard hubs d-D-l, 4-D-l' engaged (frictionally, vacuumatically etc. as shown in the art) with dielectric web M which may comprise a continuous (not discontinuous) sheet of dielectric stretched taut therebetween and adapted to be transported thereby and scanned past the imaging matrix as in the foregoing instances, these hubs being electrically neutral (of insulating material). The image-segment-defining propeller blade GP is understood as mounted on its own hub to be independently rotated and electrically charged at ground potential. Blade GP may be indexed with a prescribed segment of web M as it scans matrix plane FF and contacted therewith electrically to sweep independently, but in synchronism with M, across the imaging matrix so that the dielectric segment it then contacts may be imaged during this sweep (different segments in other sweeps, etc.). Of course, an advantage is that, since this ground propeller (and there may be a number of them, e.g. one for each quadrant) sweeps independently of the carrier hubs 4-D, it may be stepped during successive sweeping revolutions (of the hubs 4-D) to contact a different dielectric segment for each revolution (i.e. successive printline images) and sweep with it past the imaging matrix for imaging a great number of successive lines of the one dielectric web.

FIG. 5 shows a modified embodiment after the manner of FIG. 41 wherein the electrode blade (or blades) GP is adapted to have a flexible contact face or tip GP-T, such as a charged flexure blade tip adapted to resiliently bias the selected segment of web M outwardly somewhat into contact (or near adjacency) with the imaging plane FlP; e.g. wiping this segment lightly across the charging faces of the imaging electrodes and thereby ohmically charging the dielectric (by contact, unlike the noncontact ionic transfer of the foregoing cases).

FIG. 6 is a fragmentary showing of an arrangement after the manner of FIGS. 3, 4 and 5, wherein a section of a drum D is shown schematically as transporting a prescribed segment of a continuous dielectric M (eg a layer coated thereon) past a font-plane FP into imaging near-adjacency (but not contact) therewith. Between these is disposed an image mask RM adapted to rotate independently of drum D and effectively mask out all imaging transfers to medium M, save in an apertured, or windowed, section W, corresponding to the height and width of a single printline. Here, drum D is charged (unlike the embodiments of FIGS. 3' and 4). Thus, as workers in the art may visualize (and similar to the operation of the rotated ground blade GP) mask RM may be disposed with window W defining a particular imaging segment of dielectric M and swept in synchronism therewith when drum D sweeps M (past the font-plane Fl) for imaging only on the (selected printline) segment of M exposed by window W. Thereafter, in a succeeding revolution, mask RM may be indexed so that window W exposes the next adjacent selected (printline) segment of dielectric M as it sweeps past font-plane FF, and so forth for successive printline images thereon. Of course, as in the foregoing cases, a number of such windows W may be provided, such as one for each quadrant, etc.

COPY ADVANCEMENT FIG. 7 shows very schematically a copy station generally defined by copy roller 7-1, functioning as an idler roll to guide the advance of copy medium 7-CM, and a dielectric carrier drum 7-D, functioning somewhat in the manner of propeller 1-D in FIGS. 1 and 1A except for the following improvement features. Here, however, at least one pair of transport-wheels, 7-DR; 7-DR are provided, solely for copy-advance purposes (not dielectric carrying), the intermediate body of drum 7-D carrying a single row dielectric segment 7-DL (one such segment for every such wheel pair). Each such segment is operatively associated with such a pair of wheels (outboard thereof on drum 7-D) but is mechanically separate therefrom. Each such dielectric segment 7-DL may be understood as otherwise structured and operating similar to the embodiment in FIG. 2 (with only the copy station shown but the other stations being understood as before), the other elements being structured and functioning generally in the manner of FIGS. 1, IA except for the noted improvement features. Thus, as better seen in the longitudinal section of FIG. 7A, each such segment of dielectric 7-DL is intended to be imaged, toned, and then brought transferringly-adjacent the copy medium 7-CM so as to transfer the toned pattern thereto (such as with the aid of a transfer potential V if required), with or without a contact rolling transfer, etc. as before! According to this feature and modification of the invention, while such dielectric segments may be understood as functioning as indicated in FIG. 2, they are also operatively associated with their respective copy-advancing wheels (7DR,DR' for segment 7-DL). These wheels will be understood as advancing the copy medium 7-CM during the image-transfer (and/or thereafter, if desired) while being mechanically separate from the dielectric (and of not necessarily the same surface confirmation etc.) so the dielec tric will not be required to engage the copy paper 7-CM as suggested in the case of FIG. 1. Thus, although other embodiments may be visualized, according to this embodiment, each pair of copy-indexing wheels (7-DR, 7-DR) associated with a prescribed dielectric segment (7-DL) are disposed to project outwardly from the dielectric surface, toward the medium so as to engage it drivingly against idler roll 7-l, preferably, while the associated segment 7-DL is rolling past and transferring its image onto an associated line segment of medium 7-CM, such as in the manner indicated in FIG. 7A. In the illustrated embodiment, the projecting engagement-tires of wheels 7-DR, 7-DR are beveled in a prescribed manner, and oppositely, while the outer, corresponding engaging portions of idler 7-l are conformingly beveled for intimate driving engagement of the paper therebetween. Of course, as before, the length and height of each such dielectric segment 7-DL define the imaging printline portion, such as on medium 7-CM between wheels 7-DR, DR'. These wheels may be disposed circumferentially about drum 7-D so that they engage the medium 7-CM in any prescribed manner relative to the passage of an associated dielectric segment. For instance, here in the preferred embodiment wheels 7-DR, -DR engage the paper and begin to drive it just as the initial portion of the associated dielectric 7-DL begins to pass the paper 7-M in transfer relation. The wheel tires also extend somewhat downstream beyond the terminus of segment 7-DL so as to not only advance the paper during this pattern-transfer therefrom, but increment it somewhat further to establish an interline spacing, as known in the art. Other configurations will occur to those skilled in the art whereby the passage of a prescribed dielectric segment may be operatively associated with means for synchronously advancing the copy medium.

For instance, FIG. 8 indicates such a modification whereby other means are provided for advancing the copy medium in prescribed relation with the passage of the dielectric. Here, an imaging system may be understood somewhat after the fashion of FIG. 2 above including a carrier drum 8-D of prescribed diameter and including at least one dielectric segment 8-DL thereon with the imaging, toning and cleaning stations S-M, 8-TlR, 8-CL respectively functioning generally in the manner indicated in FIGS. 1 and 2. That is', an image pattern for a printline may be understood as imaged at 8-M on passingdielectric segment b-DL, toned at 8-TR and transferred to a copy medium (e.g. b-CM on copy drum 8-CD) at copy station fl-C defined at the nip between carrier drum 8-D and copy drum 8-CD. This embodiment will be understood as structured and operated in the aforeindicated manner except for the modification features now noted. That is, according to another feature of the invention, a copy drum 8-CD is provided to engage copy documents (e.g. up-coming sheet 8-CM) a prescribed length, and to advance them in prescribed transfer relation with one or more dielectric segments 8-DL on drum 8-D. in this feature the two-drums are adapted to cooperate so as to, effectively, step the paper for printout of successive lines thereon in addition to establishing a transfer station therebetween. For instance, copy drum 8-CD may be assumed to include a vacuumatic system (or other hold" means, not shown, but conventional) for wrapping each copy document (e.g. S-CM' shown) thereon to circulate it repeatedly past this drum nip (or transfer zone T-T), being mechanically coupled to be driven in synchronism with drum 8-D (conventionally, such as through timing belt 8-L) so that a common rotational drive (not shown but conventional) rotates both drums synchronously at the same surface velocity. With such an arrangement and an imaging drum 8-D having a prescribed circumference, the circumference of copy drum 8-CD may be arranged to correspond to that of drum 8-D less a single printline distance. Thus it will be apparent to those skilled in the art that a document such as 8-CM' carried on drum 8-CD may accept a prescribed line of print (line 01) from segment 8-DL and be recirculated about 8-CD to reappear at the transfer zone T-T and present the medium surface for the next line of print (line 02) in transfer relation with segment 8-DL (now reimaged) during its next revolution (for printing in a top-to-bottom mode for the reverse mode the circumference of copy drum 8-CD will be made one line larger than that of drum 8-D.

Workers in the art will appreciate the advantages of such a medium-advancing/recirciulating arrangement and will visualize other comparable ways of implementing it. For instance, regardless of the circumference of copy drum 8-CD, a gearing arrangement in the mechanical coupling may effect the same result, etc. When a full page of information has been transferred to a given document 8-CM, it is then released from drum 8-CD and transferred downstream (e.g. like infeed" rolls 84 for further treatments (e.g. fixing) storage and the like. For instance, it will be apparent that in an alternate construction, two dielectric segments may bedisposed on drum 8-D, in which case the circumference of drum 8-CD may be made one printline less than the distance between each of these dielectric segments.

FIG. 9 shows, in a rather idealized, fragmented view, an alternate imaging station embodiment including an exemplary dielectric-carrying propeller arm 9-D presenting an associated single row dielectric segment 9-DL thereon for imaging by a modified print-image station PR including a modified character-electrode matrix (type wheels wh-l through wh-n), this arrangement functioning after the manner of FIG. 1 above except in respect of the improvement features here noted. Unlike the foregoing arrangements, here the dielectric segment 9-DL is intended to be advanced into registry with a prescribed imaging plane and stopped there, this plane being defined by the nearest-adjacency of each wheel wh with the path of the dielectric. More particularly, here, each (columnregistering) set of character electrodes is modified to be formed as an array of raised font electrode faces on a single conductive-type wheel wh of known construction and controlled in a known manner so that when each particular wheel is charged to transfer-potential, the proper selected character face will be presented to that dielectric column (e.g. for wh-l, column C-l on 9-D) for imaging thereon. According to a prime aspect of this feature, each wheel wh is adapted to be so charged in a novel manner without contacting conductor means. Thus, print-imaging station PR in FIG. 9 may be viewed as comprising a plurality of conductive, endless-web electrode strips arrayed about a driven type wheel, (Le. strips on rotating wheels as opposed to the stationary concave strips aforedescribed), these strips being'directed in column registry past the imaging plane and kept electrically isolated from one another, (e.g. by mounting them to be driven in common by insulative shaft SH). It will be understood that this alternate imaging station is quite different from those aforedescribed and not adapted for cooperation with the foregoing central, focused rotary. However, it will indicate another employment for the rotary arm (propeller) type of dielectric carrier. That is, in this embodiment the imaging electrode array PR preferably comprises a stacked, insulated set of type wheels wh-l etc. of conductive material adapted to be selectively charged when a prescribed character thereon is passing the designated imaging plane lR-lR for inducing an image on the dielectric in the foregoing manner. Thus, one print wheel wh is provided at each column (such as wheel wh-l at column C-l, through wheel wit-l0 at column C-lO) all stacked in electrical isolation and character-alignment on a common shaft SH to be rotated in synchronism thereby (by means conventional but not shown). It will be apparent that, if each wheel is selectively charged at a time corresponding to the passage of a selected character thereon through the imaging plane, the

proper dielectric imaging can be effected as understood in the art.

Workers in the art may especially appreciate that, although other charging means may be used to so charge wheels wh (such as conventional slipring contacts, etc.), according to a preferred feature, this charging is effected by individual capacitive strips E associated with each such character wheel wh (e.g. E-l for charging wh-l, etc.). More particularly, if, at the prescribed character-select time, a prescribed electrical charge is applied to a strip E, disposed in prescribed capacitively-coupled relation with the passing surface of an associated print wheel wh, then a momentary charging pulse can be induced on this surface. Such a charging may, of course, induce an electrostatic image (esi) on the associated dielectric column location, this image corresponding to the selected character (type-face then passing) without any ohmic contact with the wheel. This effect of such capacitive coupling charging is better understood with reference to the exemplary operation as follows (referring to the timing diagram in FIG. 9A). Thus, waveform e-l will be understood as reflecting charging voltage pulses applied to illustrative charge strip E-l (by conventional means, not shown, including charactersynchronizing; dielectric responsive control means), while waveform w-l reflects the voltage state of associated type wheel wh-l; and similarly for waveforms e-2, w-Z for elements 5-2 and wh-2, respectively. The showing along axis F represents the registration of type font (for all wheels wh) along image-plane lR-lR. Thus, at time t the A font is passing in image registry and, since'a charging pulse e-l is then applied to charge strip E-l, a responsive (opposite polarity) pulse will then appear on associated wheel wh-l, thus inducing an A esi on column C-1 of dielectric 9-D; no other column, evidently, being so imaged (e.g. strip 5-2 for column C-2 is not then charged). During interval t the wheel set will be understood as rotated until, at time i the next row of character font (the B font) is image-registered. At this time a B esi will be understood as induced only on the column (3-2 portion of dielectric segment 9-D, since the corresponding type wheel wh-2 is then charged by its associated (capacitively coupled) charge strip 15-12 (as with E-l at time t,

Where many of the prior embodiments indicated a character-electrode imaging matrix with a relatively straightforward layout, such as matrix l-M in FIG. 1 comprised of column-electrode strips l-M-l, l-M-Z etc. arranged in sideby-side relation, this may, instead, take other forms such as a staggered form, according to another feature of the invention illustrated in FlG. it). I-Iere,-a concave array of electrode strips ill-m is staggered vertically (that is, in the direction of dielectric advancement) and by groups, each of these groups sharing a common control (select-driver) unit. For instance, in this very schematic, plan view a few exemplary groups of adjacent electrode strips (e.g. strips lll-M-l, ll-M-Z, 11-M-3 in one group) will be understood as vertically staggered within each group so as to come into image-registration with a passing (scanning) dielectric segment (idealistically and fragmentarily indicated as scanning segment IM-SG successively, all such strips in each group sharing a common select-driver. This arrangement may be understood as constructed and operated in the manner of the foregoing embodiments, except for the noted modification features. Here, each group of strip electrodes may be viewed connected in parallel to share (that is, be controlled in common by) a common control unit CSD as indicated in the schematic layout. Thus, for instance, control -unit CS-ll) may be understood as generally performing the functions of comparable control means in FIG. 1, namely the select, control and column driver functions, etc. Of three portions, of stage 1-CS, doing so for the three electrode strips llM-1l, 11-M-2, ll-M-Zi for columns I, 2 and 3 sharingly and energizing them at different successive times while dielectric segment IM-SG passes. Thus, it will be understood, for instance, that as the dielectric segment IM-SG begins to scan past the first character electrode strip 1l-M-l, a select signal ss will be applied to associated, shared, control unit CS-D to, in turn, energize electrode strip ll-M-l at a time corresponding to registry of the dielectric at the selected character thereon (as in the foregoing embodiments), the strobing control signals CCG being applied as in the foregoing cases and a shift control for commutation, etc. providing selective con nection with the first printline in Memory (during this initial scan time, the second-line and third-line signals being successively, and individually, accessed during their later respective scan times also). Thereafter, and similarly as segment IM-SC begins the scan of the second strip in this group ll-M-Z, the appropriate print signals ss therefor will be applied to unit CS-D, to be compared, as before, with strobe signals CCS for image-charging of strip ll-M-Z at the proper character-registration time (and similarly for the third strip il-M-3 in this group). Column strips 11-M-4, 5, -6 similarly share CSD etc. Of course, it will be apparent to those skilled in the art that more or less such electrode strips in a group may be shared by a common control unit, consistent with the dictates of imaging speed, of space about the periphery of the dielectric carrier, with the requirements and availability of control switching, access to memory, and the like. Workers in the art will appreciate how significant are the advantages of this shared control/multicolumn feature, such as the tremendous simplification, savings etc. in control elements.

A somewhat related sharing feature is taught by the embodirnent in FIG. ii, a staggered array of electrostatic imaging electrodes (M-ll etc. through M-NN) connected in parallel to share a single common select-driver unit CS-D in the manner of the foregoing embodiment except where otherwise indicated. Here, it will be assumed that each electrode, such as lVl-ll, M-22 etc., comprises a raised font blockshaped, all alike, to generate a single (e.g. such as a bar, a dot or like mark as used on electrostatic graph recorders, strip recorders or the like). The position of each electrode block will reference on the intersection of a respective column and row along a curved electrode plane MP, (e.g. electrode M-lll at the intersection of column (1-1 and row r-l, etc.). Here, a dielectric segment IM'-SG is understood as swept past each electrode successively (rather than past each multicharacter strip as above) and a control unit CS-DM provided to energize all the electrodes in common each time any one of them is indicated (by hit signals SS) for imaging manner of the foregoing embodiment except where otherwise indicated. Here it will be assumed that each electrode, such as M-ll, M-22, etc., comprises a raised font block-shaped, all alike, to generate a single common symbol (e.g. such as a bar", a dot or like mark as used on electrostatic graph recorders, strip recorders or the like). The position of each electrode block will reference on the intersection of a respective column and row along a curved electrode plane MP (e.g. electrode M-ll at the intersection of column C-ll and row R-1, etc.). Here, a dielectric segment IM'-SG is understood as swept past each electrode successively (rather than past each multicharacter strip as above) and a control unit CS-SM provided to energize all the electrodes in common each time any one of them is indicated (by hit signals SS) for energizing on the passing segment IMSG. In this way a single unit may control the charging of all electrodes (e.g. for the associated column of the passing dielectric segment. The passing of this dielectric segment will effect vertical-scan mechanically (as before) and may be strobe-synchronized (e.g. for registration and successive counting, shifting purposes) by a conventional means such as in the foregoing examples applying strobe signals ST to unit CS-DM. Thus, it will be apparent to those skilled in the art that besides using various features of the subject invention for printing alphanumeric symbols, various other embodiments may be applied to Tesi-print" like uniform marks of one type, such as for strip recorders and the like.

According to a subfeature of this feature, the imaging matrix MP (or mark-recording head) may lend itself to some advantageous fabrication techniques and structural features. For instance, as indicated in FIG. 11A, a fabrication profile MP may be assembled from which such a recording head MP may be constructed, quite conveniently and inexpensively. For instance, an array of insulator strips (e.g. fibrous boards B-l, B-Z etc.) may be each provided with a prescribed (e.g. printed) conductive segment CC across the width thereof to protrude at one side (a connector end) and to present, at the opposite end, a prescribed electrode face (M-ll' shaped to the desired mark configuration in its cross section). If these boards B1, B2, B3 etc. are assumed as all alike in this construction (except for the location of the conductor) and are stacked so that these connectors are staggered" diagonally to be disposed at positions corresponding to the location of electrodes M-ll etc. in FIG. 12 a proper profile MP may be formed. That is, boards B may be affixed together (such as by cementing, etc.) in this relationship with conductor faces M-ll, M-22' etc. disposed as shown, with a common conductive plate li-CP attached to the board-array in ohmic conductive relation with all the conductor segments CC (at the connector end) and provided with a terminal COM, (where at charging time 11-6 may be connected), etc. to form the finished indicated charge-headprofile MP from which a head like MP may be formed. Now, with these printed circuit boards etc. so arranged, a prescribed curved machining operation may be performed having a prescribed radius (e.g. along the concave plane suggested by machining limits FIN-FIN) the configuration of the head MP suggested in FIG. I2 may be readily rendered, as visualized by those skilled in the art. Workers in the art will be especially impressed not only with the ease of manufacturing such a head, but also with the extremely low cost of the select-driving electronics associated with this array of electrodes according to the invention.

In summary, it will be evident that the aforedescribed invention features provide improved electroprinting arrangements including novel electrostatic imaging arrangements, dielectric arrangements and associated carrier means and segmented image control means, associated transport and charging means, as well as novel improved imaging electrode arrangements, ground electrode arrangements and the like. In particular, we have taught novel, centrally disposed buffer dielectric means for accepting esi patterns and presenting them for treatment to various peripheral stations. Propeller-type dielectric carriers and ground electrode blades are also taught as well as image defining ground elec trodes on a sector of a drum periphery. Staggered esi electrode arrays are taught, together with associated shared control means. Workers in the art will recognize that modifications and rearrangement of the foregoing novel features may be contemplated within the scope of the claims. For instance, it will be recognized that the feature of electrostatic printing with a centrally disposed dielectric and a concave planar array of imaging electrodes may be yet within contemplation of the following claims.

While in accordance with the provisions of the patent statutes, there have been illustrated and described the best forms' of the invention known, it will be apparent to those skilled in the art that changes may be made in the apparatus described without departing from the spirit of the invention as set forth in the appended claims, and that, in some cases, certain features of the invention may be used to advantage, or modified, or substituted for, without a corresponding change in related features.

We claim:

1. In an electrostatic imaging arrangement including at least one imaging means adapted to generate a prescribed set of electrostatic images along a prescribed imaging locus and also including respective image-treatment means arranged in operative association with each said imaging means for treatment of the electrostatic images induced thereby, the improvement comprising; buffer dielectric means including a rotationally mounted cylindrical drum having at least one segmented dielectric printline sector therealong for receiving and storing electrostatic images, and transport means adapted to advance carrier surface means about a closed-loop transport path, for receiving images induced by said imaging means and presenting them for treatment at said associated treatment means, and indexing means comprising projected shoe means associated with each said dielectricsector, said shoe means being arranged at one, or both, outer ends of said sector and arranged to frictionally contact an associated copy web for stepping advancement thereof in prescribed relation with the passing sector.

2. The combination as recited in claim 1 wherein each said projecting shoe means comprises a pair of index shoes projected radially out at each end of a respective dielectric sector segment on said drum; said shoes being circumferentially disposed at the same sectorial location as said respective segment and extending somewhat therebeyond, for advancing a copy web an interline increment as well, synchronous with the segment passing a respective web segment portion.

3. ln an electrostatic imaging arrangement including at least one imaging means comprising a matrix of electrostatic electrodes adapted to generate a prescribed set of electrostatic images along a prescribed imaging plane and also including respective image-treatment means arranged in operative association with each said imaging means for treatment of the electrostatic images induced thereby, the improvement comprising; buffer .dielectric means including transport means comprising a rotatable substantially nonconductive drum on which a layer of dielectric is disposed to receive such electrostatic images and ground electrode means disposed substantially coperipheral with said drum and rotatable therewith, said drum and said dielectric means being arranged to, separately or together, define at least one line-segment of dielectric having a length and a height corresponding to the dimensions of a prospective line of print and each said print line segment of dielectric being adapted to be mechanically scanned past said matrix in selectable imaging relation therewith to facilitate energization control-selection of elec' trodes in this height direction.

4. The combination as recited in claim 3 wherein a plurality of such ground electrode means are provided, each being disposed on said drum and arranged and controllably-energized so as to be presented in energized relation with the said imaging plane, and any other associated treatment means along said transport path, at a particular exclusive time.

5. The combination as recited in claim 3 wherein each of said ground electrode means comprises a separately rotatable propeller blade rotatable within the longitudinal confines of said carrier drum to present its electrode periphery in imageinducing relation with the web carried by said drum, and closely adjacent to a respective segment portion thereof on the radially-inward side.

6. The combination as recited in claim 5 wherein each said blade is additionally provided with a flexible peripheral electrode surface adapted to urge a respective contacted segment portion of said dielectric outward from said carrier drum into better imaging relation with said imaging plane.

7. In an electrostatic imaging arrangement including at least one imaging means comprising a matrix ofelectrostatic electrodes adapted to generate a prescribed set of electrostatic images along a prescribed imaging plane and also including respective image-treatment means arranged in operative association with each said imaging means for treatment of the electrostatic images induced thereby, the improvement comprising: I

buffer dielectric means including dielectric printline segments and transport means comprising a rotatable drum having a continuous dielectric surface coating thereon; and

a printline defining mask means interposed between said dielectric surface and said imaging plane and separately rotatable with said drum, said mask means including an aperture portion therein for defining each said dielectric printline segments, said mask means being adapted to effectively interdict the transfer of said electrostatic images except through said printline aperture, each said printline segment of dielectric being adapted to be mechanically scanned past said matrix in selectable imaging relation therewith.

8. In an electrostatic imaging arrangement including at least one imaging means comprising a matrix of electrostatic electrodes adapted to generate a prescribed set of electrostatic images along a prescribed imaging locus and also including respective image-treatment means arranged in operative association with each said imaging means for treatment of the electrostatic images induced thereby, the improvement comprising; buffer dielectric means including dielectric web. segments adapted to receive such electrostatic images and also transport means adapted to advance carrier surface means about a closed-loop transport path and adapted to advance such segments thereon, about at least a portion of this path, for receiving images induced by said imaging means and presenting them for treatment at said associated treatment means, these means being disposed along this path with said transport means serving substantially as a focus about which all these means are arrayed in prescribed operative relation with such buffer dielectric carried thereby, said matrix of electrodes further comprising a set of like alphameric tesi-print" strips comprising, each, a set of alphameric electrode patterns in common print-row registry and prescribed print alignment with a passing web segment, such strips being effective to operate across a plurality of adjacent print-columns comprising a group of sharing column electrode sets, each set on such a strip being staggered from its neighbor to effect respective column registry so that strip sections are offset from columnto-column to register parallel set-location sections with a respective column of said segment, each said multicolumn imaging strip being connected to be controlled by a common, shared energizing means so that electrode energization may be shared between columns for each such multicolumn strip as it is shared between rows on a single strip.

9. In an electrostatic imaging arrangement including at least one imaging means comprising a matrix of electrostatic electrodes adapted to generate a prescribed set of electrostatic images along a prescribed imaging locus and also including respective image treatment means arranged in operative as sociation with each said imaging means for treatment of the electrostatic images induced thereby, the improvement comprising; buffer dielectric means including dielectric web segments adapted to receive such electrostatic images and also transport means adapted to advance carrier surface means about a closed-loop transport path andadapted to advance such segments thereon, about at least a portion of this path, for receiving images induced by said irnaging means and presenting them for treatment at said associated treatment means, these means being disposed along this path with said transport means serving substantially as a focus about which all these means are arrayed in prescribed operative relation with such bufier dielectric carried thereby, said electrode matrix being adapted for single mark imaging and comprising a plurality of like-pattern electrodes, the imaging surface of each being conformed to a prescribed common mark pattern and disposed to be presented in imaging relation with a passing dielectric segment, all of said electrodes being mounted in common electrically on a single counting means and connected to be energized in common by a single shared select-driver means, mounting means being arranged so that the electrodes are disposed across the imaging plane in staggered, continuous relation across successive column axes, so as to register each successive electrode at a different row column intersection on said imaging plane; whereby imaging signals from this common shared driver means may control all said electrodes in common, being synchronized with the mechanical scanning passage of said dielectric segment to induce an electrostatic mark-image synchronous with the passing of corresponding segment-columns.

10. The combination as recited in claim 9 wherein said imaging matrixis constructed to be fabricated from a composite bonded array of nonconductive circuit boards, each having a single conductor strip disposed thereon to present said common mark pattern along an edge thereof, these boards being arranged with these edges presented along a common plane and the said mark-defining portions of each disposed in staggered-row alignment; the boards then being bonded together and provided with common conductor means interconnecting all said conductor strips.

11. The structure as recited in claim 10 wherein said bonded boards are additionally machined to define a prescribed concave imaging plane along which said markdefiningstripends are presented for imaging the passing dielectric segments.

12. In an electrostatic imaging arrangement including at least one imaging means comprising a matrix of electrostatic electrodes adapted to generate a prescribed set of electrostatic images along a prescribed imaging plane, the improve ment comprising; a buffer including transport means adapted to advance a nonconductive carrier surface about a closed loop transport path, a layer of dielectric disposed on said surface to receive such electrostatic images and ground electrode means disposed substantially coplanar with said carrier surface beneath said layer, and movable with said surface, said carrier surface and said dielectric layer being arranged to separately or together, define at least one line segment of dielectric having a length and a heightcorresponding to the dimensions of a prospective line of print and each said print line segment of dielectric being adapted to be mechanically scanned .past said matrix in selectable imaging relation therewith to facilitate energization control-selection of electrodes in this height direction.

13. The combination as recited in claim 12 wherein said transport means includes carrier means comprising a propeller arm and wherein each said printline segment is defined by a discrete strip of dielectric coating on the surface of said carri er means.

14. The combination as recited in claim 12 wherein said transport means comprises a rotating cylindrical carrier means; wherein each said printline segment is defined by a discrete strip of dielectric coating on the surface of said carrier.

15. The combination recited in claim 14 wherein said carrier means comprises a drum; and wherein copy-drum transport means is additionally provided to advance copy sheet webs into copy-transfer re tron with each said dielectric sector at a prescribed copy-station; this copy drum being adapted to be rotated in common with said dielectric-carrier drum and dimensioned so that a continuous revolution thereof spaces a carried copy web a prescribed circumferential spacing from the prior contact-line with a respective dielectric sector, this spacing corresponding to the height of a printline, this arrangement thereby facilitating automatic copy-advancement synchronous with dielectric drum rotation.

16. The combination as recited in claim 12 wherein said transport means comprises a drum carrying said dielectric as a coating thereon to be advanced along a prescribed cylindrical path, wherein at least two such concave imaging planes are provided by a pair of respective matrices and an associated set of treatment stations is arranged in prescribed relation with a respective matrix about said cylindrical path; and drum being adapted to sweep said continuous dielectric coating thereon along said path in prescribed operative relation with these matrices and stations.

17. The combination as recited .in claim l6-wherein said imaging planes are arranged about said path so that when a prescribed printline sector of said dielectric is swept past one said matrix, a second corresponding sector will be swept, correspondingly, past said second matrix in like manner; said matrices being provided with common energization-control means.

18. The combination as recited in claim 12 wherein each said electrode matrix comprises a row of electrically-common imaging strips arranged at corresponding print-positions across a passing printline locus, each strip being arranged to be energized at a time corresponding to the passage of said dielectric sector at a selected character-electrode portion of that strip and thus quite simply providing a single shared" energization-select drive arrangement for each column of electrodes. t

19. The combination as recited in claim 18 .wherein each said strip is adapted for electrostatic recording and includes a spaced array of raised font electrode patterns registered in prescribed print-alignment with said passing segment.

20. The combination as recited in claim 19 wherein said strips comprise a set of like alphameric 'Tesi-print" strips comprising, each, a set of alphameric electrode patterns in common print-row registry. 

1. In an electrostatic imaging arrangement including at least one imaging means adapted to generate a prescribed set of electrostatic images along a prescribed imaging locus and also including respective image-treatment means arranged in operative association with each said imaging means for treatment of the electrostatic images induced thereby, the improvement comprising; buffer dielectric means including a rotationally mounted cylindrical drum having at least one segmented dielectric printline sector therealong for receiving and storing electrostatic images, and transport means adapted to advance carrier surface means about a closed-loop transport path, for receiving images induced by said imaging means and presenting them for treatment at said associated treatment means, and indexing means comprising projected shoe means associated with each said dielectric sector, said shoe means being arranged at one, or both, outer ends of said sector and arranged to frictionally contact an associated copy web for stepping advancement thereof in prescribed relation with the passing sector.
 2. The combination as recited in claim 1 wherein each said projecting shoe means comprises a pair of index shoes projected radially out at each end of a respective dielectric sector segment on said drum; said shoes being circumferentially disposed at the same sectorial location as said respective segment and extending somewhat therebeyond, for advancing a copy web an interline increment as well, synchronous with the segment passing a respective web segment portion.
 3. In an electrostatic imaging arrangement including at least one imaging means comprising a matrix of electrostatic electrodes adapted to generate a prescribed set of electrostatic images along a prescribed imaging plane and also including respective image-treatment means arranged in operative association with each said imaging means for treatment of the electrostatic images induced thereby, the improvement comprising; buffer dielectric means including transport means comprising a rotatable substantially nonconductive drum on which a layer of dielectric is disposed to receive such electrostatic images and ground electrode means disposed substantially coperipheral with said drum and rotatable therewith, said drum and said dielectric means being arranged to, separately or together, define at least one ''''line-segment'''' of dielectric having a length and a height corresponding to the dimensions of a prospective line of print and each said print ''''line segment'''' of dielectric being adapted to be mechanically scanned past said matrix in selectable imaging relation therewith to facilitate energization control-selection of electrodes in this height direction.
 4. The combination as recited in claim 3 wherein a plurality of such ground electrode means are provided, each being disposed on said drum and arranged and controllably-energized so as to be presented in energized relation with the said imaging plane, and any other associated treatment means along said transport path, at a particular exclusive time.
 5. The combination as recited in claim 3 wherein each of said ground electrode means comprisEs a separately rotatable propeller blade rotatable within the longitudinal confines of said carrier drum to present its electrode periphery in image-inducing relation with the web carried by said drum, and closely adjacent to a respective segment portion thereof on the radially-inward side.
 6. The combination as recited in claim 5 wherein each said blade is additionally provided with a flexible peripheral electrode surface adapted to urge a respective contacted segment portion of said dielectric outward from said carrier drum into better imaging relation with said imaging plane.
 7. In an electrostatic imaging arrangement including at least one imaging means comprising a matrix of electrostatic electrodes adapted to generate a prescribed set of electrostatic images along a prescribed imaging plane and also including respective image-treatment means arranged in operative association with each said imaging means for treatment of the electrostatic images induced thereby, the improvement comprising: buffer dielectric means including dielectric printline segments and transport means comprising a rotatable drum having a continuous dielectric surface coating thereon; and a printline defining mask means interposed between said dielectric surface and said imaging plane and separately rotatable with said drum, said mask means including an aperture portion therein for defining each said dielectric printline segments, said mask means being adapted to effectively interdict the transfer of said electrostatic images except through said printline aperture, each said printline segment of dielectric being adapted to be mechanically scanned past said matrix in selectable imaging relation therewith.
 8. In an electrostatic imaging arrangement including at least one imaging means comprising a matrix of electrostatic electrodes adapted to generate a prescribed set of electrostatic images along a prescribed imaging locus and also including respective image-treatment means arranged in operative association with each said imaging means for treatment of the electrostatic images induced thereby, the improvement comprising; buffer dielectric means including dielectric web segments adapted to receive such electrostatic images and also transport means adapted to advance carrier surface means about a closed-loop transport path and adapted to advance such segments thereon, about at least a portion of this path, for receiving images induced by said imaging means and presenting them for treatment at said associated treatment means, these means being disposed along this path with said transport means serving substantially as a focus about which all these means are arrayed in prescribed operative relation with such buffer dielectric carried thereby, said matrix of electrodes further comprising a set of like alphameric ''''tesi-print'''' strips comprising, each, a set of alphameric electrode patterns in common print-row registry and prescribed print alignment with a passing web segment, such strips being effective to operate across a plurality of adjacent print-columns comprising a group of sharing column electrode sets, each set on such a strip being staggered from its neighbor to effect respective column registry so that strip sections are offset from column-to-column to register parallel set-location sections with a respective column of said segment, each said multicolumn imaging strip being connected to be controlled by a common, shared energizing means so that electrode energization may be shared between columns for each such multicolumn strip as it is shared between rows on a single strip.
 9. In an electrostatic imaging arrangement including at least one imaging means comprising a matrix of electrostatic electrodes adapted to generate a prescribed set of electrostatic images along a prescribed imaging locus and also including respective image treatment means arranged in operative association with each said imaging means for treatment of the electrostatic images induced therebY, the improvement comprising; buffer dielectric means including dielectric web segments adapted to receive such electrostatic images and also transport means adapted to advance carrier surface means about a closed-loop transport path and adapted to advance such segments thereon, about at least a portion of this path, for receiving images induced by said imaging means and presenting them for treatment at said associated treatment means, these means being disposed along this path with said transport means serving substantially as a focus about which all these means are arrayed in prescribed operative relation with such buffer dielectric carried thereby, said electrode matrix being adapted for single mark imaging and comprising a plurality of like-pattern electrodes, the imaging surface of each being conformed to a prescribed common mark pattern and disposed to be presented in imaging relation with a passing dielectric segment, all of said electrodes being mounted in common electrically on a single counting means and connected to be energized in common by a single shared select-driver means, mounting means being arranged so that the electrodes are disposed across the imaging plane in staggered, continuous relation across successive column axes, so as to register each successive electrode at a different row column intersection on said imaging plane; whereby imaging signals from this common shared driver means may control all said electrodes in common, being synchronized with the mechanical scanning passage of said dielectric segment to induce an electrostatic mark-image synchronous with the passing of corresponding segment-columns.
 10. The combination as recited in claim 9 wherein said imaging matrix is constructed to be fabricated from a composite bonded array of nonconductive circuit boards, each having a single conductor strip disposed thereon to present said common mark pattern along an edge thereof, these boards being arranged with these edges presented along a common plane and the said mark-defining portions of each disposed in staggered-row alignment; the boards then being bonded together and provided with common conductor means interconnecting all said conductor strips.
 11. The structure as recited in claim 10 wherein said bonded boards are additionally machined to define a prescribed concave imaging plane along which said mark-defining strip ends are presented for imaging the passing dielectric segments.
 12. In an electrostatic imaging arrangement including at least one imaging means comprising a matrix of electrostatic electrodes adapted to generate a prescribed set of electrostatic images along a prescribed imaging plane, the improvement comprising; a buffer including transport means adapted to advance a nonconductive carrier surface about a closed loop transport path, a layer of dielectric disposed on said surface to receive such electrostatic images and ground electrode means disposed substantially coplanar with said carrier surface beneath said layer, and movable with said surface, said carrier surface and said dielectric layer being arranged to separately or together, define at least one ''''line segment'''' of dielectric having a length and a height corresponding to the dimensions of a prospective line of print and each said print ''''line segment'''' of dielectric being adapted to be mechanically scanned past said matrix in selectable imaging relation therewith to facilitate energization control-selection of electrodes in this height direction.
 13. The combination as recited in claim 12 wherein said transport means includes carrier means comprising a propeller arm and wherein each said printline segment is defined by a discrete strip of dielectric coating on the surface of said carrier means.
 14. The combination as recited in claim 12 wherein said transport means comprises a rotating cylindrical carrier means; wherein each said printline segment is defined by a discrete strip of dielectric coating on the surface of said carrier.
 15. The cOmbination recited in claim 14 wherein said carrier means comprises a drum; and wherein copy-drum transport means is additionally provided to advance copy sheet webs into copy-transfer relation with each said dielectric sector at a prescribed copy-station; this copy drum being adapted to be rotated in common with said dielectric-carrier drum and dimensioned so that a continuous revolution thereof spaces a carried copy web a prescribed circumferential spacing from the prior contact-line with a respective dielectric sector, this spacing corresponding to the height of a printline, this arrangement thereby facilitating automatic copy-advancement synchronous with dielectric drum rotation.
 16. The combination as recited in claim 12 wherein said transport means comprises a drum carrying said dielectric as a coating thereon to be advanced along a prescribed cylindrical path, wherein at least two such concave imaging planes are provided by a pair of respective matrices and an associated set of treatment stations is arranged in prescribed relation with a respective matrix about said cylindrical path; and drum being adapted to sweep said continuous dielectric coating thereon along said path in prescribed operative relation with these matrices and stations.
 17. The combination as recited in claim 16 wherein said imaging planes are arranged about said path so that when a prescribed printline sector of said dielectric is swept past one said matrix, a second corresponding sector will be swept, correspondingly, past said second matrix in like manner; said matrices being provided with common energization-control means.
 18. The combination as recited in claim 12 wherein each said electrode matrix comprises a row of electrically-common imaging strips arranged at corresponding print-positions across a passing printline locus, each strip being arranged to be energized at a time corresponding to the passage of said dielectric sector at a selected character-electrode portion of that strip and thus quite simply providing a single ''''shared'''' energization-select drive arrangement for each column of electrodes.
 19. The combination as recited in claim 18 wherein each said strip is adapted for electrostatic recording and includes a spaced array of raised font electrode patterns registered in prescribed print-alignment with said passing segment.
 20. The combination as recited in claim 19 wherein said strips comprise a set of like alphameric ''''Tesi-print'''' strips comprising, each, a set of alphameric electrode patterns in common print-row registry. 